Our transcription: One reason geologists study groundwater is to learn how it moves beneath the Earth's surface.The area in which the water accumulates is known as the "saturated zone," and the layer above it, the "unsaturated zone."When a well is dug into the saturated zone, the groundwater will fill the lower part of the well.The water level inside the well marks the upper surface of the saturated zone.This surface is called the "water table." Where the land surface is flat, the water table beneath it is also flat.But where the land is hilly, the water table will also have an irregular surface with high or low parts roughly corresponding to the overlying topography.